1. Field of the Invention
The invention relates to a cardiac pacer for pacing a heart, in particular a human heart, wherein the pacing rate is controlled by a signal that is dependent upon physical activity or a measured physiological change in the body of a patient.
2. Related Applications
The subject matter of the present application is related to the subject matter of the following co-pending applications filed simultaneously herewith: "A Cardiac Pacer For Pacing A Heart," Elmqvist, Lekholm, Hedberg and Amundson, Ser. No. 874,597; "A Cardiac Pacer For Pacing A Heart," Lekholm and Amundson, Ser. No. 874,596; "A Cardiac Pacer For Pacing A Heart," Lekholm and Amundson, Ser. No. 874,585.
3. Description of the Prior Art
Conventional cardiac pacers of the respiration rate-responsive type are, for example, described in U.S. Pat. No. 3,593,718 and in European Patent Application No. 0,089,014. An accerlerameter rate-responsive cardiac pacer is, for example, depicted in U.S. Pat. No. 4,428,378.
One of the main difficulties with these rate-responsive cardiac pacers is that it is difficult to exactly determine different exercise stages, such as the start, duration and termination of an exercise for a patient wearing such a cardiac pacer.